The present invention relates to the art of furnaces and, more particularly, to improvements in furnace wall and furnace chamber constructions.
The present invention finds particular utility in connection with the construction of the chamber walls and removable cover of a furnace, such as a forge furnace, and accordingly is disclosed and described in detail herein in connection with such a furnace. At the same time, however, it will be appreciated that a furnace wall construction in accordance with the present invention is adapted to be used in connection with the construction of other types of furnaces as well as the construction of components for use with other types of heating chambers, such as covers for soaking pits for example.
It is of course well known that furnaces, such as forge furnaces, are constructed to provide a refractory lined chamber including a bottom wall, upright front, back and side walls, and a top wall. The bottom, back, side and top walls are defined by corresponding steel plates and linings of refractory fire brick, and the front wall is constructed of refractory material to provide an access opening or openings into the chamber. Such furnace constructions are extremely heavy due to the use of refractory brick and steel plate for the construction thereof and, for reasons including the use of such materials and construction time, are undesirably expensive. Upon start up of the furnace, considerable time is required to heat the fire brick material to reach the operating temperature for the furnace, and the fire brick has a high heat retention characteristic, whereby considerable time is required for the furnace to cool sufficiently following shut down to enable access thereto such as for maintenance. Moreover, when a leakage path occurs across the fire brick lining between the furnace chamber and the steel shell plate as the result, for example, of fractures in the refractory brick and/or the mortared joints therebetween, the shell plate is excessively heated and the heat therein attacks the anchoring for the fire brick. Thus, there is a heat loss across such fractures and potential degrading of the fire brick anchoring, both of which are undesirable and lead to increased operating and maintenance costs. Moreover, such leakage paths can be detected only from within the furnace chamber and can exist for a considerable period of time without being detected. Accordingly, frequent shut down and inspection of the lining within the chamber is necessary in an effort to minimize the latter problems by detecting and repairing fractures from within the chamber. It will be appreciated that such shut down and the time required to locate and repair fractures increases maintenance time and costs and reduces production capabilities with respect to the furnace.
With further regard to such previous furnace constructions, the front wall is generally defined by a laterally extending lintel of cast refractory blocks supported above the floor of the furnace chamber so as to define an elongate opening or openings through which workpieces are introduced into the chamber. The vertical height of such openings is determined by the height of support bricks which underlie the lintel blocks and, heretofore, adjustment of the height of the openings required the use of different size supporting bricks. Such lintel blocks are quite heavy and, accordingly, considerable time and effort is required to change the opening height when it beomes necessary or desirable to do so. Furthermore, in order to enable such manipulation of the lintel blocks, the latter necessarily have open joints therebetween providing leakage paths for heat from the furnace chamber. Still further, the blocks are massive and have a high heat retention characteristic, thus adding to the heating up and cooling down times mentioned above with regard to the fire brick linings of the furnace.
Arrangements have been provided heretofore for replaceing fire brick linings in a steel shell furnace with linings of fibrous insulating material which most often are in the form of modules of given size provided internally of the fibrous material with arrangements for attaching the modules to the steel shell. Examples of such modular constructions for this purpose are shown in U.S. Pat. Nos. 3,832,815; 3,952,470; and 4,287,839. While such use of fibrous insulating material reduces the weight of the furnace lining, it does not enable minimizing the overall weight of the wall or cover component as a result of the fact that the outer side of the furnace wall is still defined by steel plate material. Furthermore, such arrangements do not avoid the problem of hot spots at the shell due to heat paths which may develop across the insulating material, and the fact that such heat paths must be located and repaired from within the furnace. Still further, the assembly procedures with regard to installing modules are time consuming, complex and physically demanding on the part of workers. It has also been proposed heretofore, as shown in U.S. Pat. No. 3,990,203, to construct a heating chamber wall from preformed modules of fibrous insulating material and an expanded metal backing. The modules are provided with embedded anchor strips welded at their opposite ends to side support members, and the expanded metal backing is welded to the anchor strips and faces outwardly of the chamber wall. Wall units thus constructed are clamped together to provide a wall assembly which is supported by connection to support beams. While such an arrangement minimizes weight in a given wall or cover component constructed therefrom, the assembly procedure is still time consuming and expensive, the expanded metal backing does not support the insulation, and the anchoring arrangement does not provide a desired retention capability with respect to maintaining the fibrous insulating material securely in place with respect to the expanded metal member. The latter are extremely important in connection with minimizing or avoiding the creation of heat leakage paths across a heating chamber component, and minimizing maintenance or replacement operations to assure stability of the heating chamber component over periods of extended use.